Synthetic process and novel intermediates

ABSTRACT

The present disclosure describes a synthetic process and novel intermediates related to spirocyclic azetidenyl-isobenzofuran derivatives having an isothiazoline moiety, which are useful as antiparasitics.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. application Ser. No.16/775,451, filed Jan. 29, 2020 which claims priority to U.S.Provisional Application Ser. No. 62/798,735, filed Jan. 30, 2019, hereinincorporated by reference in its entirety.

FIELD OF THE INVENTION

The present disclosure describes a synthetic process and novelintermediates related to prostaglandin EP4 receptor antagonists, whichare useful in the treatment or alleviation of pain and inflammation andother inflammation-associated disorders, such as arthritis, treating orpreventing disorders or medical conditions selected from pain,inflammatory diseases and the like.

BACKGROUND

Rheumatoid arthritis (RA) is an immune-mediated, systemic inflammatorydisease that affects mainly synovial joins, with intra-articularinflammation, synovial hyperplasia and progressive degradation ofcartilage and bone. Prevalence of the disease is about 1% of thepopulation, and the disease is more frequent (and perhaps worse) inwomen than in men. There have been clear advances in the pharmacologicalmanagement of rheumatoid arthritis over the last decade, but manypatients still do not tolerate or do not respond well to the availabletherapies.

Moreover, the control and management of arthritis associated pain andinflammation in animals, such as companion animals, specifically indogs, is also an area of growing interest. Many FDA-approved drugs areavailable to treat pain associated with osteoarthritis (OA) in dogs(e.g., carprofen, firocoxib, meloxicam, deracoxib, and robenacoxib), allof which work by inhibiting cyclooxygenase enzymes. The FDA approved COXinhibitor NSAIDs for use in dogs, unless contra-indicated, areconsidered to be effective treatments for the pain associated with RA.These COX-inhibiting NSAIDs, as a class, however, carry the potentialfor adverse effects including gastrointestinal ulceration andperforation, and renal insufficiency. The Food and Drug Administration(FDA) has required language in the precaution section of the packageinserts of these drugs warning that, as a class, they may be associatedwith renal, gastrointestinal (GI), and hepatic toxicity. Specifically,labels of these drugs warn of the “potential to produce GI ulcerationand/or GI perforation”.

Prostaglandins are mediators of pain, fever and other symptomsassociated with inflammation. Especially prostaglandin E2 (PGE2) is thepredominant eicosanoid detected in inflammation conditions. In addition,it is also involved in various physiological and/or pathologicalconditions and such as hyperalgesia, uterine contraction, digestiveperistalsis, awakeness, suppression of gastric acid secretion, bloodpressure, platelet function, bone metabolism, angiogenesis or the like.

Four PGE2 receptor subtypes (EP1, EP2, EP3 and EP4) displaying differentpharmacological properties have been cloned. EP4 subtype, a Gs-coupledreceptor stimulates cAMP production, and is distributed in a widevariety of tissue suggesting a major role in PGE2-mediated biologicalevents.

Among the multiple targets involved in the pathogenesis of rheumatoidarthritis, the prostaglandin E2 receptor 4 (EP4) subtype receptor ofprostaglandin E2 (PGE2) is one of the most promising because, unlikecommon NSAIDs that inhibit the synthesis of prostaglandins, selectiveEP4 antagonists have the potential to combine immunomodulatory anddirect anti-inflammatory properties. Furthermore, the EP4 receptor inmice, humans and dogs has been cloned and characterized and the canineEP4 receptor has approximately 90% homology to the human receptor. EP4antagonists present an opportunity for a novel pharmaceutical orveterinary therapy.

Grapiprant, whose chemical name isN-[[[2-[4-(2-Ethyl-4,6-dimethyl-1H-imidazo[4,5-c]pyridin-1-yl)phenyl]ethyl]amino]carbonyl]-4methylbenzenesulfonamide, and sold under the tradename Galliprant®, is aprostaglandin E2 (PGE2) EP4 receptor antagonist; a non-cyclooxygenase(COX) inhibiting, non-steroidal anti-inflammatory drug (NSAID) in thepiprant class. Grapiprant is indicated for the control of pain andinflammation associated with osteoarthritis (OA) in dogs. Furtherreference is made to WO 2002/032422, WO 2002/032900, WO 2006/095268, aswell as WO 2003/086371, WO 2011/102149, and WO 2014/148053. Additionalbackground research regarding compounds with an imidazopyridine orimidazopyrazine core ring structure include US 2013/195848, WO2014/078813, WO 2011/151259, WO 2011/113862, US 2005/0009832, US2004/0220189, WO 2006/091671, and WO 2018/013430. All of these citedpatent publications are incorporated by reference with regard to theirbackground teaching.

Despite this background of research and development, there remains aneed for novel EP4 antagonists to offer safe and effectivepharmaceutical or veterinary therapy. PCT/US2018/046142, hereinincorporated by reference in its entirety, describes novelimidazopyridine/pyrazine derivatives with activity as prostaglandin EP4receptor antagonists. More specifically, the imidazopyridine/pyrazinederivatives, including veterinary or pharmaceutically acceptable saltsthereof, are represented by Formula (I):

whereinX is N or CR¹, where each R¹ individually is hydrogen, halogen, CN, C₁₋₃alkyl, or C₁₋₃ haloalkyl;R² is hydrogen, C₁₋₃ alkyl, or C₁₋₃ haloalkyl;R³ is hydrogen, C₁₋₃ alkyl, or C₁₋₃ haloalkyl;R⁴ is hydrogen, C₁₋₃ alkyl, C₁₋₃ haloalkyl, or C₃₋₆ cycloalkyl;R⁵ is hydrogen, halogen, CN, C₁₋₃alkyl, or C₁₋₃haloalkyl;Ar is phenyl, pyridyl, or thiophenyl, each optionally substituted withone or more halogen, CN, NO₂, NH₂, N(C₁₋₃ alkyl)₂, OH, OC₁₋₃ alkyl, C₁₋₃alkyl, or C₁₋₃ haloalkyl; and L is —CH₂CH₂—, —CH₂CH₂CH₂—, or —OCH₂C.

One embodiment described is a compound1-[2-[4-(2-ethyl-6,8-dimethyl-imidazo[1,2-a]pyrazin-3-yl)phenyl]ethyl]-3-(p-tolylsulfonyl)urea, or a veterinary or pharmaceutically acceptable salt thereof.

SUMMARY

The present disclosure describes a synthetic process for the compoundsof Formula (I) of PCT/US2018/046142, for example, in particular for thecompound1-[2-[4-(2-ethyl-6,8-dimethyl-imidazo[1,2-a]pyrazin-3-yl)phenyl]ethyl]-3-(p-tolylsulfonyl)urea, or a veterinary or pharmaceutically acceptable salt thereof.

One embodiment includes a compound selected from4-methyl-N-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenethyl)carbamoyl)benzenesulfonamide;2-ethyl-6,8-dimethylimidazo[1,2-a]pyrazine; or3-bromo-2-ethyl-6,8-dimethylimidazo[1,2-a]pyrazine, or a veterinary orpharmaceutically acceptable salt thereof. Each of these compounds isbelieved to be a useful intermediate in the synthesis of a final productuseful as an EP4 antagonist.

One embodiment includes a process for making1-[2-[4-(2-ethyl-6,8-dimethyl-imidazo[1,2-a]pyrazin-3-yl)phenyl]ethyl]-3-(p-tolylsulfonyl)ureaor a salt thereof comprising using4-methyl-N-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenethyl)carbamoyl)benzenesulfonamide.

One embodiment includes a process for making a compound of Formula (II)or a salt thereof:

wherein:X is N or CR¹, where R¹ is hydrogen, halogen, CN, C₁₋₃ alkyl, or C₁₋₃haloalkyl;R² is hydrogen, halogen, C₁₋₃ alkyl, C₁₋₃ haloalkyl, CN, aryl, orheteroaryl;R³ is hydrogen, halogen, C₁₋₃ alkyl, C₁₋₃ haloalkyl, or CN;R⁴ is hydrogen, C₁₋₃ alkyl, C₁₋₃ haloalkyl, C₃₋₆ cycloalkyl,heterocyclyl, heteroaryl, or aryl;Z is phenyl or C₃₋₇ cycloalkyl, each substituted with one or more R⁵,where R⁵ is hydrogen, halogen, CN, C₁₋₃ alkyl, C₁₋₃ haloalkyl, C₁₋₃haloalkoxy, or C₁₋₃ alkoxy;Ar is phenyl, pyridyl, or thiophenyl, each optionally substituted withone or more halogen, CN, NO₂, NH₂, N(C₁₋₃ alkyl)₂, OH, C₁₋₃ alkoxy, C₁₋₃alkyl, or C₁₋₃ haloalkyl; andL is CH₂CH₂, CH₂CH₂CH₂, or OCH₂CH₂, comprising:cyclizing a compound of formula (a):

wherein:X is N or CR¹, where R¹ is hydrogen, halogen, CN, C₁₋₃ alkyl, or C₁₋₃haloalkyl;R² is hydrogen, halogen, C₁₋₃ alkyl, C₁₋₃ haloalkyl, CN, aryl, orheteroaryl; andR³ is hydrogen, halogen, C₁₋₃ alkyl, C₁₋₃ haloalkyl, or CN; halogenatingthe resulting cyclized product to form a compound of formula (b):

wherein R⁴ is hydrogen, C₁₋₃ alkyl, C₁₋₃ haloalkyl, C₃₋₆ cycloalkyl,heterocyclyl, heteroaryl, or aryl; andtreating a compound of formula (b) with a compound of formula (c):

whereinZ is phenyl substituted with R⁵, where R⁵ is hydrogen, halogen, CN, C₁₋₃alkyl, C₁₋₃ haloalkyl, C₁₋₃ haloalkoxy, or C₁₋₃ alkoxy;Ar is phenyl, pyridyl, or thiophenyl, each optionally substituted withone or more halogen, CN, NO₂, NH₂, N(C₁₋₃ alkyl)₂, OH, C₁₋₃ alkoxy, C₁₋₃alkyl, or C₁₋₃ haloalkyl; andL is CH₂CH₂, CH₂CH₂CH₂, or OCH₂CH₂,to form a compound of Formula (II).

In one aspect, X is N, R² is C₁₋₃ alkyl, R³ is C₁₋₃ alkyl, R⁴ is C₁₋₃alkyl, Ar is phenyl, L is CH₂CH₂, Z is phenyl substituted with one R⁵.In one aspect R² is methyl, R³ is methyl, R⁴ is ethyl, Ar isunsubstituted phenyl, and R⁵ is C₁₋₃ alkyl. In one aspect, R⁵ is methyl.In one aspect, the compound of formula (c) is4-methyl-N-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenethyl)carbamoyl)benzenesulfonamide.In one aspect, the compound of Formula (II) is1-[2-[4-(2-ethyl-6,8-dimethyl-imidazo[1,2-a]pyrazin-3-yl)phenyl]ethyl]-3-(p-tolylsulfonyl)urea.

As herein described, the synthetic process herein described is useful inthe preparation of compounds that are described in U.S. ProvisionalApplication No. 62/798,738 and its progeny, which are herebyincorporated by reference in their entirety.

The compound,1-[2-[4-(2-ethyl-6,8-dimethyl-imidazo[1,2-a]pyrazin-3-yl)phenyl]ethyl]-3-(p-tolylsulfonyl)urea, which may be referred to as Compound A, is useful for treatingpain, such as one or more of joint pain, musculoskeletal pain, lowerback pain, neck pain, skeletal pain, sprain, strain, myositis,neuralgia, fibromyalgia, synovitis, arthritis, rheumatoid arthritis,degenerative joint disease, osteoarthritis, gout, ankylosingspondylitis, and bursitis. One aspect of these embodiments includeswhere the subject is a mammal. One aspect of these embodiments includeswhere the mammal is a companion animal.

One or more aspects and embodiments may be incorporated in a differentembodiment although not specifically described. That is, all aspects andembodiments may be combined in any way or combination.

DETAILED DESCRIPTION

The present disclosure describes a synthetic process for Compounds ofFormula (I) and (II), in particular, for the compound1-[2-[4-(2-ethyl-6,8-dimethyl-imidazo[1,2-a]pyrazin-3-yl)phenyl]ethyl]-3-(p-tolylsulfonyl)urea, or a veterinary or pharmaceutically acceptable salt thereof.

The preparation of Compound A or a veterinary acceptable salt thereofmay be accomplished via the route and intermediates described inPCT/US2018/046142. As an alternative for manufacturing scale, however,the preparation of compounds of Formula (I) and (II), including CompoundA, or salts thereof, may be accomplished via the route and intermediatesshown hereinbelow.

Scheme 1 describes a general process for preparing compounds of Formula(I) and (II), and specifically Compound A, wherein

X is N or CR¹, where each R¹ individually is hydrogen, halogen, CN, C₁₋₃alkyl, or C₁₋₃ haloalkyl;R² is hydrogen, C₁₋₃ alkyl, C₁₋₃ haloalkyl, halogen, CN, aryl, orheteroaryl;R³ is hydrogen, C₁₋₃ alkyl, halogen, CN, or C₁₋₃ haloalkyl;R⁴ is hydrogen, C₁₋₃ alkyl, C₁₋₃ haloalkyl, or C₃₋₆ cycloalkyl,heteroaryl, heterocyclyl, or aryl;R⁵ is hydrogen, halogen, CN, C₁₋₃ alkyl, or C₁₋₃ haloalkyl, C₁₋₃haloalkoxy, or C₁₋₃ alkoxy;Ar is phenyl, pyridyl, or thiophenyl, each optionally substituted withone or more halogen, CN, NO₂, NH₂, N(C₁₋₃ alkyl)₂, OH, OC₁₋₃ alkyl, C₁₋₃alkyl, or C₁₋₃ haloalkyl; andL is —CH₂CH₂—, —CH₂CH₂CH₂—, or —OCH₂CH₂—.

As used herein the phrase veterinary or veterinarily or pharmaceuticalor pharmaceutically acceptable salt refers to any salt of a compounddisclosed herein which retains its biological properties and which isnot toxic or otherwise undesirable for veterinary or pharmaceutical use.Certain compounds of the present invention have sites that would allowfor a veterinary or veterinarily, or pharmaceutical or pharmaceuticallyacceptable salt, and such salt forms are also included in the presentinvention. Such salts may be derived from a variety of organic andinorganic counter-ions known in the art. Such salts include: (1) acidaddition salts formed with organic or inorganic acids such ashydrochloric, hydrobromic, sulfuric, nitric, phosphoric, sulfamic,acetic, trifluoroacetic, trichloroacetic, propionic, hexanoic,cyclopentylpropionic, glycolic, glutaric, pyruvic, lactic, malonic,succinic, sorbic, ascorbic, malic, maleic, fumaric, tartaric, citric,benzoic, 3-(4-hydroxybenzoyl)benzoic, picric, cinnamic, mandelic,phthalic, lauric, methanesulfonic, ethanesulfonic,1,2-ethane-disulfonic, 2-hydroxyethanesulfonic, benzenesulfonic,4-chlorobenzenesulfonic, 2-naphthalenesulfonic, 4-toluenesulfonic,camphoric, camphorsulfonic,4-methylbicyclo[2.2.2]-oct-2-ene-1-carboxylic, glucoheptonic,3-phenylpropionic, trimethylacetic, tert-butylacetic, lauryl sulfuric,gluconic, benzoic, glutamic, hydroxynaphthoic, salicylic, stearic,cyclohexylsulfamic, quinic, muconic acid, and like acids.

Salts further include, by way of example only, salts of non-toxicorganic or inorganic acids, such as halides, such as, chloride andbromide, sulfate, phosphate, sulfamate, nitrate, acetate,trifluoroacetate, trichloroacetate, propionate, hexanoate,cyclopentylpropionate, glycolate, glutarate, pyruvate, lactate,malonate, succinate, sorbate, ascorbate, malate, maleate, fumarate,tartarate, citrate, benzoate, 3-(4-hydroxybenzoyl)benzoate, picrate,cinnamate, mandelate, phthalate, laurate, methanesulfonate (mesylate),ethanesulfonate, 1,2-ethane-disulfonate, 2-hydroxyethanesulfonate,benzenesulfonate (besylate), 4-chlorobenzenesulfonate,2-naphthalenesulfonate, 4-toluenesulfonate, camphorate,camphorsulfonate, 4-methylbicyclo[2.2.2]-oct-2-ene-1-carboxylate,glucoheptonate, 3-phenylpropionate, trimethylacetate, tert-butylacetate,lauryl sulfate, gluconate, benzoate, glutamate, hydroxynaphthoate,salicylate, stearate, cyclohexylsulfamate, quinate, muconate, and thelike.

Examples of inorganic bases that can be used to form base addition saltsinclude, but are not limited to, metal hydroxides, such as lithiumhydroxide, sodium hydroxide, and potassium hydroxide; metal amides, suchas lithium amide and sodium amide; metal carbonates, such as lithiumcarbonate, sodium carbonate, and potassium carbonate; and ammonium basessuch as ammonium hydroxide and ammonium carbonate.

Examples of organic bases that can be used to form base addition saltsinclude, but are not limited to, metal alkoxides, such as lithium,sodium, and potassium alkoxides including lithium methoxide, sodiummethoxide, potassium methoxide, lithium ethoxide, sodium ethoxide,potassium ethoxide, and potassium tert-butoxide; quaternary ammoniumhydroxides, such as choline hydroxide; and amines including, but notlimited to, aliphatic amines (i.e., alkylamines, alkenylamines,alkynylamines, and alicyclic amines), heterocyclic amines, arylamines,heteroarylamines, basic amino acids, amino sugars, and polyamines.

According to embodiments of the present invention, the base can be aquaternary ammonium hydroxide, wherein one or more of the alkyl groupsof the quaternary ammonium ion are optionally substituted with one ormore suitable substituents. Preferably, at least one alkyl group issubstituted with one or more hydroxyl groups. Non-limiting examples ofquaternary ammonium hydroxides that can be used in accordance with thepresent invention include choline hydroxide, trimethylethylammoniumhydroxide, tetramethylammonium hydroxide, and is preferably cholinehydroxide. According to embodiments of the present invention, analkylamine base can be substituted or unsubstituted. Non-limitingexamples of unsubstituted alkylamine bases that can be used inaccordance with the present invention include methylamine, ethylamine,diethylamine, and triethylamine. A substituted alkylamine base ispreferably substituted with one or more hydroxyl groups, and preferablyone to three hydroxyl groups. Non-limiting examples of substitutedalkylamine bases that can be used in accordance with the presentinvention include 2-(diethylamino)ethanol, N,N-dimethylethanolamine(deanol), tromethamine, ethanolamine, and diolamine.

As used herein, the terms “subject” and “patient” are usedinterchangeably herein. The terms “subject” and “subjects” refer to aprimate such as a monkey such as a cynomolgus monkey, a chimpanzee, anda human or non-primate animal. In one embodiment, the subject is ahuman. In another embodiment, the subject is a companion animal such asa dog or cat. In a further embodiment, the subject is an animal ofagricultural importance such as a sheep, cow, horse, goat, fish, pig, ordomestic fowl (such as a chicken, turkey, duck, or goose).

In addition, certain compounds of the present invention have substituentgroups that would allow for a pharmaceutically acceptable prodrugmoiety, and such prodrug forms are also included in the presentinvention. A pharmaceutically acceptable prodrug refers to a compoundhaving a group which may be converted into an amino group, a hydroxylgroup, a carboxyl group, or the like, by solvolysis or under aphysiological condition. Examples of the groups forming the prodruginclude those as described in Prog. Med., 5, 2157-2161 (1985) or“Pharmaceutical Research and Development” (Hirokawa Publishing Company,1990), vol. 7, Drug Design, 163-198. The term prodrug is used throughoutthe specification to describe any pharmaceutically acceptable form of acompound, which upon administration to a patient, provides the activecompound. Pharmaceutically acceptable prodrugs refer to a compound thatis metabolized, for example hydrolyzed or oxidized, in the host to formthe compound of the present invention. Typical examples of prodrugsinclude compounds that have biologically labile protecting groups on afunctional moiety of the active compound. Prodrugs include compoundsthat may be oxidized, reduced, aminated, deaminated, hydroxylated,dehydroxylated, hydrolyzed, dehydrolyzed, alkylated, dealkylated,acylated, deacylated, phosphorylated, dephosphorylated to produce theactive compound.

The present invention includes all pharmaceutically acceptableisotopically-labelled compounds of the invention wherein one or moreatoms are replaced by atoms having the same atomic number, but an atomicmass or mass number different from the atomic mass or mass numberusually found in nature. Examples of isotopes suitable for inclusion inthe compounds of the invention include isotopes of hydrogen, such as ²Hand ³H, carbon, such as ¹¹C, ¹³C and ¹⁴C, chlorine, such as ³⁶Cl,fluorine, such as ¹⁸F, iodine, such as ¹²³I and ¹²⁵I, nitrogen, such as¹³N and ¹⁵N, oxygen, such as ¹⁵O, ¹⁷O and ¹⁸O, phosphorus, such as ³²P,and sulfur, such as ³⁵S. Certain isotopically-labelled compounds of theinvention, such as those incorporating a radioactive isotope, may beuseful in drug or substrate tissue distribution studies. The radioactiveisotopes tritium, i.e. ³H, and carbon-14, i.e. ¹⁴C, are particularlyuseful for this purpose in view of their ease of incorporation and readymeans of detection. Substitution with heavier isotopes such asdeuterium, i.e. ²H, may afford certain therapeutic advantages resultingfrom greater metabolic stability, for example, increased in vivohalf-life or reduced dosage requirements, and hence may be preferred insome circumstances. Substitution with positron emitting isotopes, suchas ¹¹C, ¹⁸F, ¹⁵O and ¹³N, may be useful in Positron Emission Topography(PET) studies for examining substrate receptor occupancy.Isotopically-labelled compounds of the invention may generally beprepared by conventional techniques known to those skilled in the art orby processes analogous to those described in the accompanying Examplesand Preparations using an appropriate isotopically-labelled reagents inplace of the non-labelled reagent previously employed.

In certain cases, the depicted substituents can contribute to opticaland/or stereoisomerism. Compounds having the same molecular formula butdiffering in the nature or sequence of bonding of their atoms or in thearrangement of their atoms in space are termed “isomers.” Isomers thatdiffer in the arrangement of their atoms in space are termed“stereoisomers.” Stereoisomers that are not mirror images of one anotherare termed “diastereomers” and those that are non-superimposable mirrorimages of each other are termed “enantiomers”. When a compound has anasymmetric center, for example when it is bonded to four differentgroups, a pair of enantiomers is possible. An enantiomer can becharacterized by the absolute configuration of its asymmetric center andis designated (R) or (S) according to the rules of Cahn and Prelog (Cahnet al., 1966, Angew. Chem. 78: 413-447, Angew. Chem., Int. Ed. Engl. 5:385-414 (errata: Angew. Chem., Int. Ed. Engl. 5:511); Prelog andHelmchen, 1982, Angew. Chem. 94: 614-631, Angew. Chem. Internat. Ed.Eng. 21: 567-583; Mata and Lobo, 1993, Tetrahedron: Asymmetry 4:657-668) or can be characterized by the manner in which the moleculerotates the plane of polarized light and is designated dextrorotatory orlevorotatory (namely, as (+)- or (−)-isomers, respectively). A chiralcompound can exist as either an individual enantiomer or as a mixturethereof. A mixture containing equal proportions of enantiomers is calleda “racemic mixture”.

In certain embodiments, the compounds disclosed herein can possess oneor more asymmetric centers; and such compounds can therefore be producedas the individual (R)- or (S)-enantiomer or as a mixture thereof. Unlessindicated otherwise, for example by designation of stereochemistry atany position of a formula, the description or naming of a particularcompound in the specification and claims is intended to include bothindividual enantiomers and mixtures, racemic or otherwise, thereof.Methods for determination of stereochemistry and separation ofstereoisomers are well-known in the art.

In certain embodiments, the compounds disclosed herein are“stereochemically pure”. A stereochemically pure compound has a level ofstereochemical purity that would be recognized as “pure” by those ofskill in the art. Of course, this level of purity may be less than 100%.In certain embodiments, “stereochemically pure” designates a compoundthat is substantially free, i.e. at least about 85% or more, ofalternate isomers. In particular embodiments, the compound is at leastabout 85%, about 90%, about 91%, about 92%, about 93%, about 94%, about95%, about 96%, about 97%, about 98%, about 99%, about 99.5% or about99.9% free of other isomers.

Compositions and Methods of Administration

Compound A or a veterinary or pharmaceutically acceptable salt thereof,made in the methods disclosed herein, may be administered in certainembodiments using veterinary or pharmaceutical compositions including atleast one compound of Formula (I) or (II), if appropriate in the saltform, either used alone or in the form of a combination with one or morecompatible and veterinarily or pharmaceutically acceptable carriers,such as diluents or adjuvants, or with another agent. There are providedcompositions which comprise Compound A or a veterinary orpharmaceutically acceptable salt thereof, and an acceptable excipient,carrier, or diluent. The composition may also be in a variety of forms,including, but are not limited to, oral formulations, injectableformulations, and topical, dermal or subdermal formulations.

The composition may be in a form suitable for oral use, for example, asdietary supplements, troches, lozenges, chewables, tablets, hard or softcapsules, emulsions, aqueous or oily suspensions, aqueous or oilysolutions, dispersible powders or granules, syrups, or elixirs.Compositions intended for oral use may be prepared according to anymethod known in the art for the manufacture of veterinary,pharmaceutical, or pesticidal compositions and such compositions maycontain one or more agents selected from the group consisting ofsweetening agents, bittering agents, flavoring agents, coloring agentsand preserving agents in order to provide elegant and palatablepreparations.

Tablets may contain the active ingredient in admixture with non-toxic,pharmaceutically acceptable excipients, which are suitable for themanufacture of tablets. These excipients may be, for example, inertdiluents, such as calcium carbonate, sodium carbonate, lactose, calciumphosphate or sodium phosphate; granulating and disintegrating agents,for example, corn starch, or alginic acid; binding agents, for example,starch, gelatin or acacia, and lubricating agents, for example,magnesium stearate, stearic acid or talc. The tablets may be uncoated orthey may be coated by known techniques to delay disintegration andabsorption in the gastrointestinal tract and thereby provide a sustainedaction over a longer period.

Formulations for oral use may be hard gelatin capsules, wherein theactive ingredient is mixed with an inert solid diluent, for example,calcium carbonate, calcium phosphate or kaolin. Capsules may also besoft gelatin capsules, wherein the active ingredient is mixed with wateror miscible solvents such as propylene glycol, PEGs and ethanol, or anoil medium, for example, peanut oil, liquid paraffin, or olive oil.

The compositions may also be in the form of oil-in-water or water-in-oilemulsions. The oily phase may be a vegetable oil, for example, olive oilor arachis oil, or a mineral oil, for example, liquid paraffin ormixtures of these. Suitable emulsifying agents may be naturallyoccurring phosphatides, for example, soy bean, lecithin, and esters orpartial esters derived from fatty acids and hexitol anhydrides, forexample, sorbitan monoleate, and condensation products of the saidpartial esters with ethylene oxide, for example, polyoxyethylenesorbitan monooleate. The emulsions may also contain sweetening agents,bittering agents, flavoring agents, and preservatives.

In one embodiment of the formulation, the composition is in the form ofa microemulsion. Microemulsions are well suited as the liquid carriervehicle. Microemulsions are quaternary systems comprising an aqueousphase, an oily phase, a surfactant and a cosurfactant. They aretranslucent and isotropic liquids. Microemulsions are composed of stabledispersions of microdroplets of the aqueous phase in the oily phase orconversely of microdroplets of the oily phase in the aqueous phase. Thesize of these microdroplets is less than 200 nm (1000 to 100,000 nm foremulsions). The interfacial film is composed of an alternation ofsurface-active (SA) and co-surface-active (Co-SA) molecules which, bylowering the interfacial tension, allows the microemulsion to be formedspontaneously. In one embodiment of the oily phase, the oily phase maybe formed from mineral or vegetable oils, from unsaturatedpolyglycosylated glycerides or from triglycerides, or alternatively frommixtures of such compounds. In one embodiment of the oily phase, theoily phase comprises of triglycerides; in another embodiment of the oilyphase, the triglycerides are medium-chain triglycerides, for example,C₈-C₁₀ caprylic/capric triglyceride. In another embodiment, the oilyphase will represent a % v/v range selected from the group consisting ofabout 2 to about 15%; about 7 to about 10%; and about 8 to about 9% v/vof the microemulsion. The aqueous phase includes, for example, water orglycol derivatives, such as propylene glycol, glycol ethers,polyethylene glycols or glycerol. In one embodiment of the glycolderivatives, the glycol is selected from the group consisting ofpropylene glycol, diethylene glycol monoethyl ether, dipropylene glycolmonoethyl ether and mixtures thereof. Generally, the aqueous phase willrepresent a proportion from about 1 to about 4% v/v in themicroemulsion. Surfactants for the microemulsion include diethyleneglycol monoethyl ether, dipropylene glycol monomethyl ether,polyglycolyzed C₈-C₁₀ glycerides or polyglyceryl-6 dioleate. In additionto these surfactants, the cosurfactants include short-chain alcohols,such as ethanol and propanol. Some compounds are common to the threecomponents discussed above, for example, aqueous phase, surfactant andcosurfactant. However, it is well within the skill level of thepractitioner to use different compounds for each component of the sameformulation. In one embodiment for the amount ofsurfactant/cosurfactant, the cosurfactant to surfactant ratio will befrom about 1/7 to about 1/2.

In another embodiment for the amount of cosurfactant, there will be fromabout 25 to about 75% v/v of surfactant and from about 10 to about 55%v/v of cosurfactant in the microemulsion.

Oily suspensions may be formulated by suspending the active ingredientin a vegetable oil, for example, atachis oil, olive oil, sesame oil orcoconut oil, or in mineral oil such as liquid paraffin. The oilysuspensions may contain a thickening agent, for example, beeswax, hardparaffin or cetyl alcohol. Sweetening agents such as sucrose, saccharinor aspartame, bittering agents, and flavoring agents may be added toprovide a palatable oral preparation. These compositions may bepreserved by the addition of an anti-oxidant such as ascorbic acid, orother known preservatives.

Aqueous suspensions may contain the active material in admixture withexcipients suitable for the manufacture of aqueous suspensions. Suchexcipients are suspending agents, for example, sodiumcarboxymethylcellulose, methylcellulose, hydroxypropylmethylcellulose,sodium alginate, polvinylpyrrolidone, gum tragacanth and gum acacia;dispersing or wetting agents may be a naturally-occurring phosphatide,for example, lecithin, or condensation products of an alkylene oxidewith fatty acids, for example, polyoxyethylene stearate, or condensationproducts of ethylene oxide with long chain aliphatic alcohols, forexample, heptadecaethyleneoxycetanol, or condensation products ofethylene oxide with partial esters derived from fatty acids and ahexitol such as polyoxyethylene sorbitol monooleate, or condensationproducts of ethylene oxide, with partial esters derived from fatty acidsand hexitol anhydrides, for example, polyethylene sorbitan monooleate.The aqueous suspensions may also contain one or more preservatives, forexample, ethyl, or n-propyl, p-hydroxybenzoate, one or more coloringagents, one or more flavoring agents, and one or more sweetening agentsand/or bittering agents, such as those set forth above.

Dispersible powders and granules suitable for preparation of an aqueoussuspension by the addition of water provide the active ingredient inadmixture with a dispersing or wetting agent, suspending agent and oneor more preservatives. Suitable dispersing or wetting agents andsuspending agents are exemplified by those already mentioned above.Additional excipients, for example, sweetening, bittering, flavoring andcoloring agents, may also be present.

Syrups and elixirs may be formulated with sweetening agents, forexample, glycerol, propylene glycol, sorbitol or sucrose. Suchformulations may also contain a demulcent, a preservative, flavoringagent(s), and coloring agent(s).

The compositions may be in the form of a sterile injectable aqueous oroleagenous suspension. This suspension may be formulated according tothe known art using those suitable dispersing or wetting agents andsuspending agents which have been mentioned above. The sterileinjectable preparation may also be a sterile injectable solution orsuspension in a non-toxic parenterally-acceptable diluent or solvent,for example, as a solution in 1,3-butane diol. Among the acceptablevehicles and solvents that may be employed are water, Ringer's solutionand isotonic sodium chloride solution. Co-solvents such as ethanol,propylene glycol or polyethylene glycols may also be used.Preservatives, such as phenol or benzyl alcohol, may be used.

In addition, sterile, fixed oils are conventionally employed as asolvent or suspending medium. For this purpose, any bland fixed oil maybe employed including synthetic mono- or diglycerides. In addition,fatty acids such as oleic acid find use in the preparation ofinjectables.

Topical, dermal and subdermal formulations may include emulsions,creams, ointments, gels or pastes or ‘spot-on’ formulations.

Organic solvents that may be used in the invention include but are notlimited to: acetyltributyl citrate, fatty acid esters such as thedimethyl ester, diisobutyl adipate, acetone, acetonitrile, benzylalcohol, butyl diglycol, dimethylacetamide, dimethylformamide,dipropylene glycol n-butyl ether, ethanol, isopropanol, methanol,ethylene glycol monoethyl ether, ethylene glycol monomethyl ether,monomethylacetamide, dipropylene glycol monomethyl ether, liquidpolyoxyethylene glycols, propylene glycol, 2-pyrrolidone (e.g.N-methylpyrrolidone), diethylene glycol monoethyl ether, ethylene glycoland diethyl phthalate, or a mixture of at least two of these solvents.

As vehicle or diluent, compositions of the present invention may includeplant oils such as, but not limited to soybean oil, groundnut oil,castor oil, corn oil, cotton oil, olive oil, grape seed oil, sunfloweroil, etc.; mineral oils such as, but not limited to, petrolatum,paraffin, silicone, etc.; aliphatic or cyclic hydrocarbons oralternatively, for example, medium-chain (such as C₈-C₁₂) triglycerides.

Dosage forms may contain from about 0.5 mg to about 5 g of an activeagent.

In one embodiment of the invention, the active agent is present in theformulation at a concentration of about 0.05 to 10% weight/volume.

The compounds of Formula (I) or (II) may be employed as such or in theform of their preparations or formulations as combinations with otheractive substances, such as, for example, other such as, for example, EP4antisense nucleic acids, amino acids, peptides, carbohydrates, anti-EP4antibodies, COX-2 selective, COX-1 selective or non-selective NSAIDs,opioids, local anesthetics, disease-modifying, anti-rheumatoid drugs, orsteroids. The combinations may be part of the same formulation or may beadministered separately or sequentially to the locus.

The compounds of Formula (I) and (II) are useful for treating pain, suchas one or more of joint pain, musculoskeletal pain, lower back pain,neck pain, skeletal pain, sprain, strain, myositis, neuralgia,fibromyalgia, synovitis, arthritis, rheumatoid arthritis, degenerativejoint disease, osteoarthritis, gout, ankylosing spondylitis, andbursitis.

The compounds of Formula (I) and (II) may be combined with one or moreagents having the same sphere of activity, for example, to increaseactivity, or with substances having another sphere of activity, forexample, to broaden the range of activity. Any of the individuallylisted agents may be used in combination with compounds of Formula (I)and (II) along with any other one or more listed agents independently.

Suitable agents for combination therapy include, whereby one or morecompounds of Formula (I) and (II) may be employed as such or in the formof their preparations or formulations as combinations with one or moreother veterinary or pharmaceutically active substances, such as, forexample, EP4 antisense nucleic acids, amino acids, peptides,carbohydrates, anti-EP4 antibodies, COX-2 selective, COX-1 selective ornon-selective NSAIDs, opioids, local anesthetics, disease-modifying,anti-rheumatoid drugs, or steroids. The combinations may be part of thesame formulation or may be administered separately or sequentially.

A pharmaceutical preparation comprising a compound of Formula (I) and(II), for example, Compound A or a veterinary or pharmaceuticallyacceptable salt thereof for delivery to a human or other mammal, ispreferably in unit dosage form, in which the preparation is subdividedinto unit doses containing an appropriate quantity of the activecomponent. The unit dosage form may be a packaged preparation containingdiscrete quantities of the preparation, such as packaged tablets,capsules, and powders in vials or ampoules. Also, the unit dosage formmay be a capsule, tablet or lozenge itself, or it may be an appropriatenumber of any of these in packaged form.

The quantity of active component in a unit dose preparation may bevaried or adjusted from about 0.1 mg to about 1000 mg, according to theparticular application and the potency of the active component. Thecomposition may, if desired, also contain other compatible therapeuticagents.

In therapeutic use for the treatment or prevention of pain in a human orother mammal, the compounds utilized in the method of treatment areadministered at an initial dosage of about 0.1 mg/kg to about 100 mg/kgper interval. Preferred intervals may be daily, weekly, semi-monthly,monthly, bi-monthly, quarterly, tri-annually, semi-annually, orannually. The dosages may be varied depending on the requirements of thepatient, for example, the size of the human or mammal being treated, theseverity of the condition being treated, the route of administration,and the potency of the compound(s) being used. Determination of theproper dosage and route of administration for a particular situation iswithin the skill of the practitioner. Generally, the treatment will beinitiated with smaller dosages which are less than the optimum dose ofthe compound, which may be increased in small increments until theoptimum effect under the particular circumstances is reached. Forconvenience, the total daily dosage may be divided and administered inportions during the day if desired.

Compound A, and compositions comprising a therapeutically effectiveamount of Compound A, an acceptable salt thereof, and a veterinary orpharmaceutically acceptable excipient, diluent, or carrier are useful asmethod for treating pain comprising administering to a subject in needthereof an effective amount of a compound of the present invention.Additionally, Compound A may be used in therapy. Additionally, CompoundA may be useful in the manufacture of a medicament for the treatment ofpain. Additionally, Compound A may be used for the treatment of pain.One aspect of these embodiments includes where the subject is a mammal.One aspect of these embodiments includes where the mammal is a companionanimal. One aspect of these embodiments includes where the pain isassociated with one or more of joint pain, musculoskeletal pain, lowerback pain, neck pain, skeletal pain, sprain, strain, myositis,neuralgia, fibromyalgia, synovitis, arthritis, rheumatoid arthritis,degenerative joint disease, osteoarthritis, gout, ankylosingspondylitis, and bursitis.

Compound A or a veterinary or pharmaceutically acceptable salt thereof,or a suitable combination of Compound A or a veterinary orpharmaceutically acceptable salt thereof and optionally, with at leastone additional veterinary or pharmaceutical agent may be administereddirectly to the animal and/or indirectly by applying it to the localenvironment in which the animal dwells (such as bedding, enclosures, andthe like). Direct administration includes contacting the skin, fur, orfeathers of a subject animal with the compound(s), or by feeding orinjecting the compounds into the animal.

EXAMPLES

Experimental Procedures:

Liquid chromatography—mass spectrometry (LCMS) experiments to determineretention times and associated mass ions were performed using one ormore of the following Methods A, B, and C:Method A: Waters BEH (ethylene bridged hybrid) C₁₈ column, 3.0×30 mm,1.7 μm, was used at a temperature of 50° C. and at a flow rate of 1.5mL/min, 2 μL injection, mobile phase: (A) water with 0.1% formic acidand 1% acetonitrile, mobile phase; (B) MeOH with 0.1% formic acid;retention time given in minutes. Method A details: (1) ran on a BinaryPump G1312B, Agilent Technologies, with UV/Vis diode array detectorG1315C and Agilent 6130 mass spectrometer in positive and negative ionelectrospray mode with UV PDA detection with a gradient of 15-95% (B) ina 2.2 min linear gradient (II) hold for 0.8 min at 95% (B) (III)decrease from 95-15% (B) in a 0.1 min linear gradient (IV) hold for 0.29min at 15% (B);Method B: An Agilent Zorbax Bonus RP column, 2.1×50 mm, 3.5 μm, was usedat a temperature of 50° C. and at a flow rate of 0.8 mL/min, 2 μLinjection, mobile phase: (A) water with 0.1% formic acid and 1%acetonitrile, mobile phase (B) MeOH with 0.1% formic acid; retentiontime given in minutes. Method B details: (1) ran on a Binary PumpG1312B, Agilent Technologies, with UV/Vis diode array detector G1315Cand Agilent 6130 mass spectrometer in positive and negative ionelectrospray mode with UV-detection at 220 and 254 nm with a gradient of5-95% (B) in a 2.5 min linear gradient (II) hold for 0.5 min at 95% (B)(III) decrease from 95-5% (B) in a 0.1 min linear gradient (IV) hold for0.29 min at 5% (B).Method C: An API 150EX mass spectrometer, Applied Biosystems, linked toa Shimadzu LC-10AT liquid chromatography system, with a diode arraydetector was used. The spectrometer had an electrospray source operatingin positive and negative ion mode. The liquid chromatography was carriedout using an Agilent ZORBAX XDB 50×2.1 mm C₁₈ column and a 0.5 mL/minuteflow rate. Method C details: Solvent A: 95% water, 5% acetonitrilecontaining 0.01% formic acid; Solvent B: acetonitrile. The gradient wasshown 0-0.5 min: 2% solvent (B); 0.5-2.5 min: 2% solvent B to 95%solvent (B); 2.5-4.0 min: 95% solvent (B); 4.0-4.2 min: 95% solvent (B)to 2% solvent B; 4.2-6.0 min: 2% solvent (B).

Experimental Details

Example 1

4-methyl-N-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenethyl)carbamoyl)benzenesulfonamide

Reaction run in a 12 L 4 neck round bottom flask equipped with athermowell, reflux condenser and N₂ inlet. To a cooled (<8° C.) solutionof 4-bromophenethyl amine (291 g, 1.45 mol) in 2-MeTHF (5.82 L, 20 vol)was added p-tolylsulfonyl isocyanate (222 mL, 1.45 mol) at a rate thatkept the internal temperature below 15° C. After internal temperaturebegan cooling again (˜5 min.), the ice bath was removed and reaction wasallowed to stir at room temperature. After 16 h, it was noticed that thetubing attaching the stir shaft to the overhead stirrer failed. Thefailed piece of equipment was replaced, and the resultant mixture wasallowed to stir for 22 h at room temperature. The reaction atmospherewas flushed with a stream of nitrogen for 20 min. before potassiumacetate (428 g, 4.36 mol) was added. The mixture was degassed bybubbling N₂ through it for 2.5 h. Bis(pinacolato)diboron (443 g, 1.75mol) and Cl₂Pd(dppf).CH₂Cl₂ (59.4 g, 72.7 mmol) were added. The reactionatmosphere was flushed with nitrogen for 15 min. before the mixture wasfurther degassed by bubbling nitrogen through it for 45 min. Reactionwas heated to 80° C. for 19 h under an atm. of N₂. Activated charcoal(303 g) was added and heating at 80° C. continued for 2 h beforeinternal temperature was adjusted to 40° C. The warm (40° C.) mixturewas filtered on a Buchner funnel and rinsed with 2-Me THF (5.82 L). Theorganic solution was extracted 3×1.94 L 10% aq. NaOH and pH of combinedalkaline aq. fractions was adjusted to 5.03 (measured with a 3 pointcalibrated pH meter) with 6 molar aq. HCl (2.8 L) and 10% aq. NaOH (157mL). The aq. layer and glassware were extracted 3×1.94 L EtOAc. Thecombined organic fractions were washed 1×1.94 mL saturated aq. NaCl,dried with Na₂SO₄ filtered and stored at room temperature for 9 h. Theorganic solution was concentrated in vacuo to give 681 g of a black tarthat was stored at room temperature for 63 h. Tar was dissolved in hot(65° C.) EtOAc (1.36 L, 2 vol) and transferred to a 4 neck 12 L roundbottom flask equipped with an overhead stirrer, addition funnel andthermowell coupled to a J-KEM/heating mantel. Internal temperature wasadjusted to 65° C. and hot (65° C.) heptane (3 L, 4.4 vol) was added(over 45 min.) until solids were observed forming. The solution wasseeded and the temperature of the J-KEM was adjusted to 55° C. Onceinternal temperature cooled to 55° C., stirring was continued for 1 hbefore additional hot (55° C.) heptane (475 mL) was added (over 40 min.)until solids were observed forming. Solution was seeded and thetemperature of the J-KEM was adjusted to 45° C. After 25 min. a whitesuspension was observed and internal temperature was observed to be 44°C. The power to the heating mantel was turned off and the mixture wasallowed to slowly to room temperature while stirring. After 9 h themixture was filtered on a Buchner funnel and solids were rinsed withheptane (2.4 L). The solids were left to dry in the Buchner funnel whilethe vacuum was still pulling air for 6 h to give 398 g of a white solid.The solid was found to be ˜93% by weight (HPLC area @ 220 nm andcalculated response factor). Actual amount of4-methyl-N-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenethyl)carbamoyl)benzenesulfonamidewas 370 g (57% yield) as a white solid. ¹H NMR (400 MHz, CHLOROFORM-d)δ=7.78 (d, J=8.0 Hz, 2H), 7.55 (d, J=8.4 Hz, 2H), 7.27-7.16 (m, 4H),6.61-6.54 (m, 1H), 3.55-3.48 (m, 2H), 2.84 (t, J=6.8 Hz, 2H), 2.44 (s,3H), 1.36 (s, 12H). LC/MS RT=1.35 min., 445.2 [M+H]⁺

2-ethyl-6,8-dimethylimidazo[1,2-a]pyrazine HBr salt

To a solution of 2-amino-3,5-dimethyl pyrazine (112 g, 0.910 mol) int-BuOH (1.7 L, 15 vol) was added 1-bromo-2-butanone (175 mL, 80% byweight, 1.36 mol). Reaction was heated to 80° C. for 19 h before thesolution was cool to 30° C. and diluted with MTBE (1.7 L). Suspensionwas filtered on a Buchner funnel and solids rinsed with heptane (1.2 L).Filter cake was dried in the Buchner funnel under vacuum for 2 h to give179 g of 2-ethyl-6,8-dimethylimidazo[1,2-a]pyrazine HBr salt (77%) as apink solid. ¹H NMR (400 MHz, DMSO-d₆) δ=8.58 (s, 1H), 8.23 (s, 1H), 2.89(q, J=7.6 Hz, 2H), 2.83 (s, 3H), 2.50 (s, 3H), 1.32 (t, J=7.6 Hz, 3H).

2-ethyl-6,8-dimethylimidazo[1,2-a]pyrazine

To a solution of saturated aq. NaHCO₃ (1.7 L) was added2-ethyl-6,8-dimethylimidazo[1,2-a]pyrazine HBr salt (173 g, 674 mmol)portion wise over 3 min. The reaction was stirred at room temp for 30min. before reaction was diluted with EtOAc (1 L) and saturated aq. NaCl(1 L). The organic layer was separated and the aq. layer was extracted2×1 L EtOAc. The combined organic layers were washed 1×1 L saturated aq.NaCl, dried with Na₂SO₄, filtered and concentrated in vacuo to give 85.8g of 2-ethyl-6,8-dimethylimidazo[1,2-a]pyrazine. The aq. fraction wasre-extracted 3×1 L EtOAc and the combined organic fractions were washed1×1 L saturated aq. NaCl, dried with Na₂SO₄, filtered and concentratedin vacuo to give an additional 29.7 g of2-ethyl-6,8-dimethylimidazo[1,2-a]pyrazine. Total of 116 g (98%) of2-ethyl-6,8-dimethylimidazo[1,2-a]pyrazine was isolated. ¹H NMR (400MHz, CHLOROFORM-d) δ=7.71 (s, 1H), 7.34 (s, 1H), 2.91-2.84 (m, 5H), 2.46(d, J=0.8 Hz, 3H), 1.36 (t, J=7.6 Hz, 3H). LC/MS RT=0.19 min., 176.2[M+H]⁺

3-bromo-2-ethyl-6,8-dimethylimidazo[1,2-a]pyrazine

To a solution of 2-ethyl-6,8-dimethylimidazo[1,2-a]pyrazine (116 g, 659mmol) in AcOH (1.73 L, 15 vol) was added bromine (33.8 mL, 659 mmol).Reaction stirred at room temperature for 1 h then concentrated in vacuoto remove 1.2-1.4 L of acetic acid. Slurry was diluted with water (0.7L) to obtain a solution. The pH was adjusted (measured with a 3 pointcalibrated pH meter) from 1.11 to 7.12 with aq. NaOH (3.0 L, 10% by wt).The aq. solution was extracted 3×1 L EtOAc and the combined organicfractions were washed 1×500 mL saturated aq. NaCl, dried with Na2SO4,filtered and concentrated in vacuo to give 164 g of3-bromo-2-ethyl-6,8-dimethylimidazo[1,2-a]pyrazine (98%). 1H NMR (400MHz, CHLOROFORM-d) δ=7.70 (s, 1H), 2.90-2.82 (m, 5H), 2.53 (s, 3H), 1.35(t, J=7.6 Hz, 3H). LC/MS RT=0.61 min., 256.2 [M+H]⁺.

1-[2-[4-(2-ethyl-6,8-dimethyl-imidazo[1,2-a]pyrazin-3-yl)phenyl]ethyl]-3-(p-tolylsulfonyl)urea

Reaction run in a 4 neck 12 L round bottom flask equipped with anoverhead stirrer, thermowell, reflux condenser and N₂ inlet. A solutionof 3-bromo-2-ethyl-6,8-dimethylimidazo[1,2-a]pyrazine (171 g, 99.7% bywt, 671 mmol) and4-methyl-N-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenethyl)carbamoyl)benzenesulfonamide(322 g, 93% by weight, 671 mmol) in 2-Me THF (6 L, 20 vol) was degassedby bubbling N₂ through it for 5 hour. Cs₂CO₃ (658 g, 2.02 mol) andCl₂Pd(dppf).CH₂Cl₂ (27.5 g, 33.6 mmol) were added and degassing wascontinued for 1 h. Reaction heated to reflux for 40 h before it wasallowed to cool. When internal temperature dropped to 35° C., water (3L) was added and mixture stirred until a biphasic solution was obtained.The 2-Me THF layer was separated and the pH of the aq. layer wasadjusted (measured with a 3 point calibrated pH meter) from 9.66 to 5.03with 6 molar aq. HCl (550 mL) and 1 molar aq. NaOH (55 mL). The aq.layer and glassware were extracted 4×2 L EtOAc. The EtOAc fractions werecombined with the 2-Me THF fraction and the organic solution was washedsaturated aq. NaCl (˜25% volume of organic solution), dried with Na₂SO₄(˜100 g/L solution), filtered and concentrated in vacuo. The solutionprecipitated a black/brown solid during the last 6-8 L of solvent duringthe concentration and 455 g of a brown/black solid was obtained. Flaskthat contained solid was flushed with nitrogen, sealed with a septum andstored at room temperature for 64 h. Isolated solids were transferred toa 3 neck 5 L round bottom flask equipped with an overhead stirrer andthermowell coupled to a heating mantel. The solid was suspended ini-PrOH (1.1 L) and heated to 55° C. with stirring for 45 min. before theheating manel was removed and allowed to cool to 27° C. over 1.5 h withstirring. The suspension was reheated to 55° C. for 45 min. before theheat was turned off to the heating mantel and the suspension allowed toslowly cool to room temperature with stirring over 15 h. The suspensionwas subjected to the same heat/cool cycle, with stirring, an additional3 times before heat was turned off to heating mantel and mixture allowedto cool to room temperature over 17 h. Stirring was discontinued andsuspension was filtered on a Buchner funnel. The isolated cake wasrinsed with heptane (0.35 L). The top of the Buchner funnel was fittedwith a sealed cover that fed nitrogen while the solid dried for 20 hunder the vacuum applied. Isolated 266 g of1-[2-[4-(2-ethyl-6,8-dimethyl-imidazo[1,2-a]pyrazin-3-yl)phenyl]ethyl]-3-(p-tolylsulfonyl)urea(80%) as a brown solid. The ¹H NMR observed 13 mol % pinacol □=1.20,along with 2.7 mol % EtOAc and 1.5 mol % i-PrOH contaminants. HPLCpurity R.T.=5.66 min., 96.2584% at 220 nm and 98.9164% at 254 nm. ¹H NMR(400 MHz, METHANOL-d₄) δ=7.83-7.77 (m, 3H), 7.39 (s, 4H), 7.33 (d, J=8.0Hz, 2H), 4.10 (q, J=7.1 Hz, 1H), 3.95-3.89 (m, 1H), 3.43 (t, J=6.9 Hz,2H), 2.89-2.76 (m, 7H), 2.39 (s, 3H), 2.35 (s, 3H), 2.02-2.00 (m, 1H),1.28 (t, J=7.6 Hz, 3H), 1.20 (s, 2H), 1.15 (d, J=6.2 Hz, 1H). ICP-OESfor Pd observed 2983 ppm Pd.

Slurry Purification.

In a 3 neck 5 L round bottom flask equipped with an overhead stirrer andthermowell coupled to a heating mantel was added1-[2-[4-(2-ethyl-6,8-dimethyl-imidazo[1,2-a]pyrazin-3-yl)phenyl]ethyl]-3-(p-tolylsulfonyl)urea(262 g) and EtOAc (2.61 L, 10 vol). Mixture was heated and stirred for45 min at 50° C. before it was allowed to cool to 25° C. by removingheating mantel. Stirring was then continued at room temp for 45 min.before the heat cool cycle was repeated 2 additional times. The lastcooling operation allowed to stir at room temp for 16 h. The heat coolcycle was repeated 2 additional times. The last cooling operationallowed to stir at room temp for 18 h. The mixture was filtered on aBuchner funnel. The top of the Buchner funnel was fitted with a sealedcover that fed nitrogen while the solid dried for 23 h under the vacuumapplied. Isolated 206 g (79%) of1-[2-[4-(2-ethyl-6,8-dimethyl-imidazo[1,2-a]pyrazin-3-yl)phenyl]ethyl]-3-(p-tolylsulfonyl)ureaas a brown solid. The ¹H NMR observed 4 mol % EtOAc and 0.25 mol %pinacol contaminants.

HPLC purity R.T.=5.67 min., 97.3690% at 220 nm and 99.1957% at 254 nm.ICP-OES for Pd observed 2021 ppm Pd. ¹H NMR (400 MHz, METHANOL-d₄)δ=7.83-7.77 (m, 3H), 7.39 (s, 4H), 7.33 (d, J=8.2 Hz, 2H), 4.10 (q,J=7.1 Hz, 1H), 3.43 (t, J=7.0 Hz, 2H), 2.88-2.77 (m, 7H), 2.39 (s, 3H),2.35 (s, 3H), 2.01 (s, 1H), 1.28 (t, J=7.6 Hz, 3H), 1.20 (s, 1H). LC/MSRT=0.91 min., 492.2 [M+H]⁺. Anal Calcd for1-[2-[4-(2-ethyl-6,8-dimethyl-imidazo[1,2-a]pyrazin-3-yl)phenyl]ethyl]-3-(p-tolylsulfonyl)urea(factoring in EtOAc and pinacol): C, 63.46; H, 5.97; N, 14.13; S, 6.47.Found: C, 63.41; H, 5.84; N, 13.84; S, 6.36. ICP-OES for Pd observed2021 ppm Pd.

Palladium remediation of1-[2-[4-(2-ethyl-6,8-dimethyl-imidazo[1,2-a]pyrazin-3-yl)phenyl]ethyl]-3-(p-tolylsulfonyl)urea

NaHSO₃ (900 g) was dissolved in DI water (3.6 L) and a portion (2.71 L,15 vol) was transferred into a 3 neck 5 L round bottom flask equippedwith an overhead stirrer.1-[2-[4-(2-ethyl-6,8-dimethyl-imidazo[1,2-a]pyrazin-3-yl)phenyl]ethyl]-3-(p-tolylsulfonyl)urea(186 g) was added and additional aq. NaHSO₃ (1 L) was used to rinse allthe1-[2-[4-(2-ethyl-6,8-dimethyl-imidazo[1,2-a]pyrazin-3-yl)phenyl]ethyl]-3-(p-tolylsulfonyl)ureainto the aq. mixture in the flask. Mixture was vigorously stirred for 20min before all the dry1-[2-[4-(2-ethyl-6,8-dimethyl-imidazo[1,2-a]pyrazin-3-yl)phenyl]ethyl]-3-(p-tolylsulfonyl)ureawas mixed within the aq. layer. Stirring continued for 2 h before the pHof the mixture was adjusted from 3.69 to 5.01 with aq. NaOH (215 mL, 2molar). The mixture was extracted 3×5.7 L EtOAc and the organic layerswere stored in amber 4 L bottles for 17 h. The organic layer wasextracted 1×10% volume saturated aq. NaCl, dried with Na₂SO₄ (250 g/4 Lsolution), filtered through celite and concentrated in vacuo to give 173g of a tan solid. A portion of the solid (657 mg) at this stage wasseparated and shipped for testing by ICP-OES for Pd. The remaining solidwas dissolved in DCM/EtOH (3.45 L, 2:1) and transferred to a 3 neck 5 Lround bottom flask equipped with an overhead stirrer. Silamet thiol(17.2 g, 1.36 mmol/g, 40-63 □m) was added and the mixture stirred atroom temperature for 24 h. Mixture was filtered through a Buchner funneland resultant solution was filtered through a Meisnner filter (0.45 mm).Meisnner filter was rinsed with DCM/EtOH (0.3 L, 2:1) and organicsolution was concentrated in vacuo to give 183 g of1-[2-[4-(2-ethyl-6,8-dimethyl-imidazo[1,2-a]pyrazin-3-yl)phenyl]ethyl]-3-(p-tolylsulfonyl)ureaas a tan solid. The 1H NMR observed 5.5 mol % DCM and 98 mol % EtOHgiving an actual yield of 167 g (90% recovery) of1-[2-[4-(2-ethyl-6,8-dimethyl-imidazo[1,2-a]pyrazin-3-yl)phenyl]ethyl]-3-(p-tolylsulfonyl)urea.HPLC purity RT=5.81 min., 96.4616% at 220 nm and 99.0221% at 254 nm.ICP-OES for Pd, for sample obtained prior to treatment with thiol resin,observed 176 ppm Pd. ICP-OES for Pd, for final sample obtained, observed41 ppm Pd. ¹H NMR (400 MHz, METHANOL-d₄) δ=7.84-7.77 (m, 3H), 7.39 (s,4H), 7.36-7.31 (m, 2H), 5.49 (s, 1H), 3.61 (q, J=7.1 Hz, 2H), 3.43 (t,J=7.0 Hz, 2H), 2.88-2.77 (m, 7H), 2.39 (d, J=0.8 Hz, 3H), 2.35 (s, 3H),1.28 (t, J=7.6 Hz, 3H), 1.18 (t, J=7.1 Hz, 3H).

Abbreviations used herein fall within accepted use and should beinterpreted accordingly.

All publications, patents and patent applications cited in thisspecification are incorporated herein by reference for the teaching towhich such citation is used.

The specific responses observed may vary according to and depending onthe particular active compound selected or whether there are presentcarriers, as well as the type of formulation and mode of administrationemployed, and such expected variations or differences in the results arecontemplated in accordance with practice of the present invention.

Although specific embodiments of the present invention are hereinillustrated and described in detail, the invention is not limitedthereto. The above detailed descriptions are provided as exemplary ofthe present invention and should not be construed as constituting anylimitation of the invention. Modifications will be obvious to thoseskilled in the art, and all modifications that do not depart from thespirit of the invention are intended to be included with the scope ofthe appended claims.

We claim:
 1. A compound selected from:4-methyl-N-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenethyl)carbamoyl)benzenesulfonamide; 2-ethyl-6,8-dimethylimidazo[1,2-a]pyrazine; and3-bromo-2-ethyl-6,8-dimethylimidazo[1,2-a]pyrazine, or a veterinary orpharmaceutically acceptable salt thereof.
 2. A method of treating pain,the method comprising the step of: administering to a mammal in needthereof a therapeutically effective amount of a compound of Formula (II)or veterinary or pharmaceutically acceptable salt thereof:

wherein: X is N or CR¹, where R¹ is hydrogen, halogen, CN, C₁₋₃ alkyl,or C₁₋₃ haloalkyl; R² is hydrogen, halogen, C₁₋₃ alkyl, C₁₋₃ haloalkyl,CN, aryl, or heteroaryl; R³ is hydrogen, halogen, C₁₋₃ alkyl, C₁₋₃haloalkyl, or CN; R⁴ is hydrogen, C₁₋₃ alkyl, C₁₋₃ haloalkyl, C₃₋₆cycloalkyl, heterocyclyl, heteroaryl, or aryl; Z is phenyl substitutedwith R⁵, where R⁵ is hydrogen, halogen, CN, C₁₋₃ alkyl, C₁₋₃ haloalkyl,C₁₋₃ haloalkoxy, or C₁₋₃ alkoxy; Ar is phenyl, pyridyl, or thiophenyl,each optionally substituted with one or more halogen, CN, NO₂, NH₂,N(C₁₋₃ alkyl)₂, OH, C₁₋₃ alkoxy, C₁₋₃ alkyl, or C₁₋₃ haloalkyl; and L isCH₂CH₂, CH₂CH₂CH₂, or OCH₂CH₂.
 3. The method of claim 2, wherein themammal is a companion animal.
 4. The method of claim 2, wherein the painis selected from the group consisting of joint pain, musculoskeletalpain, lower back pain, neck pain, skeletal pain, sprain, strain,myositis, neuralgia, fibromyalgia, synovitis, arthritis, rheumatoidarthritis, degenerative joint disease, osteoarthritis, gout, ankylosingspondylitis, and bursitis.
 5. The method of claim 2, wherein X is N, R²is C₁₋₃ alkyl, R³ is C₁₋₃ alkyl, R⁴ is C₁₋₃ alkyl, Ar is phenyl, L isCH₂CH₂, and Z is phenyl substituted with one R⁵.
 6. The method of claim5, wherein R² is methyl, R³ is methyl, R⁴ is ethyl, Ar is unsubstitutedphenyl, and R⁵ is C₁₋₃ alkyl.
 7. The method of claim 6, wherein R⁵ ismethyl.
 8. The method of claim 7, wherein the compound of Formula (II)is1-[2-[4-(2-ethyl-6,8-dimethyl-imidazo[1,2-a]pyrazin-3-yl)phenyl]ethyl]-3-(p-tolylsulfonyl)urea.9. The method of claim 2, wherein the therapeutically effective amountof a compound of Formula (II) or veterinary or pharmaceuticallyacceptable salt thereof is combined with a veterinary orpharmaceutically acceptable excipient, diluent, or carrier.
 10. Themethod of claim 2, wherein the therapeutically effective amount of acompound of Formula (II) or veterinary or pharmaceutically acceptablesalt thereof is formulated as an oral formulation, injectableformulation, topical formulation, dermal formulation, or subdermalformulation.
 11. The method of claim 10, wherein the oral formulation isa dietary supplement, troche, lozenge, chewable, tablet, hard or softcapsule, emulsion, aqueous or oily suspension, aqueous or oily solution,dispersible powder, dispersible granule, syrup, or elixir.
 12. Themethod of claim 2, wherein the step of administering to a mammal in needthereof includes directly introducing the therapeutically effectiveamount of a compound of Formula (II) or veterinary or pharmaceuticallyacceptable salt thereof to the mammal via contact with skin, fur, orfeathers.
 13. The method of claim 12, wherein directly introducing thetherapeutically effective amount of a compound of Formula (II) orveterinary or pharmaceutically acceptable salt thereof includes feedingor injecting the mammal.
 14. The method of claim 2, wherein the step ofadministering to a mammal in need thereof includes indirectlyintroducing the therapeutically effective amount of a compound ofFormula (II) or veterinary or pharmaceutically acceptable salt thereofto the mammal via contact with a local environment in which the mammaldwells.
 15. The method of claim 2, wherein the therapeutically effectiveamount of a compound of Formula (II) or veterinary or pharmaceuticallyacceptable salt thereof is present in a formulation at a concentrationof about 0.05 to 10% weight/volume.
 16. The method of claim 2, whereinthe therapeutically effective amount of a compound of Formula (II) orveterinary or pharmaceutically acceptable salt thereof is administereddaily, weekly, semi-monthly, monthly, bi-monthly, quarterly,tri-annually, semi-annually, or annually.